`W_(O_(2))=8 g`
Moles of `O_(2)=8/32=1/4`
`W_(H_(2))=4 g`
Moles of `H_(2)=4/2=2`
Total moles present in mixture `=1/4+2=9/4`
Volume of vessel `=1 dm^(3)=1 L`
Temperature `=27^(@)C=27+273=300 K`
Now for pressure of mixture `=PxxV=nxxRT`
`Pxx1=9/4xx0.083xx300`
`P=56.025 "bar"`